Although some of the characters have been there since the very beginning, most of the performers behind the lovable Muppets ofSesame Street have changed over the course of the show’s nearly 50-year run. The one constant through five decades was Caroll Spinney, the puppeteer behind two of the show’s signature characters: Oscar the Grouch and Big Bird. Even as Sesame Street changed networks, changed time slots, changed human sidekicks, Spinney endured. But with the show approaching its 50th season, Spinney has announced he will finally retire. Sesame Street’s original Big Bird is flying away.

Big Bird and Oscar aren’t leaving the show, of course; new performers will assume the parts. (In the case of Big Bird, he’ll be portrayed by Matt Vogel, who has been Spinney’s understudy since 1996 and recently also inherited the role of Kermit the Frog.) But the character will never be the same without Spinney, who is credited with developing Big Bird’s lovable, child-like personality over the course of the show’s early years. (Big Bird was originally conceived, per Spinney in a new interview with The New York Times, as “a funny, dumb country yokel.”)

Later this week, Spinney will record his voice voices for Oscar and Big Bird. (The 84-year-old Spinney stopped puppeteering the characters in 2015 after developing problems with his balance.) Those recordings will air next year as part of Sesame Street’s 50th anniversary celebration. It is, at least, an impressive milestone with which to make a curtain call. Spinney told the Times that playing Big Bird for 50 years was “one of the most joyous things of my life.” For more on Spinney’s life — and to see just how difficult it is to play Big Bird — check out the recent documentary about Spinney, I Am Big Bird, which is currently available for rent.